I found this in the last Backup Technique magazine, from 1994. Apparently it's a Neo Geo interlacing circuit, though I've never tried it out. The article says it's only good for the Neo, and it's only good on computer monitors, not TVs. I'm not sure why, perhaps 'cause it's working on composite sync, and the circuit doesn't cover re-integration with the video?
(http://gamesx.com/grafx/NeoInterlaceT.png) (http://gamesx.com/grafx/NeoInterlace.png)
Note too that the 74LS221 seems to have a different pinout from every manufacturer. The pins above are based on the schematic, but the labels may be incorrect. The pins I used were taken from the pinout for a Philips 74LS221 (http://gamesx.com/grafx/74221.pdf). None of the others seemed to match at all...
Looks interesting... I noticed that the circuit diagram does not specify Vcc (power). Is this right?
So, would it allow for a pseudo 31.5kHz composite sync? Or would it just turn 240p RGB into 480i RGB? If the article specifies that it only works with the Neo Geo, perhaps it would work with any other "240p" signal... Hmm.... I'm tempted to build one of these, but the diagram doesn't look right...